Objective system comprising a principal objective and a four-component attachment



Sept. 20, 1966 K. MACHER ET AL 3,273,457

OBJECTIVE SYSTEM COMPRISING A PRINCIPAL OBJECTIVE AND A FOUR-COMPONENT ATTACHMENT Filed May 12, 1964 2 Sheets-Sheet l KARL MACHER RUDOLF SOLISCH WALTER WOLTCHE Jn vemarr.

1w by C g AGENT HUUIJ Sept. 20, 1966 K. MACHER ET AL 3,273,457

OBJECTIVE SYSTEM COMPRISING A PRINCIPAL OBJECTIVE AND A FOUR-COMPONENT ATTACHMENT Filed May 12, 1964 2 Sheets-Sheet 2 KARL MACHER RUDOLF SQLISCH WALTER WOLTCHE Jnvenfors.

AGENT United States Patent 3 273,457 OBJECTIVE SYSTEM COMPRISING A PRINCIPAL OBJECTIVE AND A FOUR-COMPONENT AT- TACHMENT Karl Macher, Bad Kreuznach, Rudolf Solisch, Gottmgen,

and Walter Wiiltche, Bad Kreuznach, Germany, assignors to Josef Schneider & Co., Optische Werke, Bad Kreuznach, Rhineland, Germany Filed May 12, 1964, Ser. No. 366,878 Claims priority, application Germany, May 14, 1963, Sch 33,278 11 Claims. (CI. 88-57) This application is a continuation-in-part of our co pending application Ser. No. 209,866, filed July 16, 1962, now abandoned. I

The present invention relates to varifooal objectives of the type comprising a multilens basic objective and a four-component front attachment therefor, with two stationary and positively refracting outer lens members (of which the more forward one may be limitedly displaceable for focusing purposes) bracketing two movable and negatively retracting inner lens members, as disclosed in commonly assigned application Ser. No. 159,392 filed November 14, 1961, by Rudolf Solisch and Walter Woltche, and now abandoned.

Heretofore a varifocal objective of this type has been realizable with aperture ratios up to approximately 122.8 and varifocal ratios of about 1:33. The general object of this invention is to improve both ratios.

A more specific object of the instant invention is to provide a varifocal objective of this character which can be opened up to a relative aperture of about 1:1.8 and whose effective focal length can be varied in the range of at least 1:4, with high-quality optical performance particularly in the region of the shorter focal lengths (wideangle range) and with compact design.

A further, more particular object of our present invention is to provide an objective in which the aforestated desiderata are fulfilled and wherein, at the same time, the displacement stroke of the movable negative components is reduced in comparison with the arrangement disclosed in our aforementioned application Ser. No. 209,866, now abandoned, whereby the total axial length of the system is decreased and, in addition, the position of the entrance pupil will be shifted to allow for the use of lenses of smaller diameter for the first two object-side components.

A feature of the objective to which the present invention pertains, as disclosed in our copending application, is that the second component of the attachment as seen from the object side of the system, i.e., the more forward one of the axially movable negative components, is of higher power than the remaining components of the attachment and, in particular, has an individual focal length which is less than twice the focal length of the basic ob jective associated with the attachment; the latter focal length is generally equal to the mean focal length of the entire system.

According to another feature of such objective, designed to afford particularly good correction of chromatic aberrations over the entire varifocal range, the first two components of the attachment are doublets with strongly refractive cemented surfaces. In particular it has been found advantageous to make the cemented surface of the first movable component (i.e., the second component of the attachment) positively refracting with a radius whose absolute magnitude is'less than 2.5 times that of the radius of the concave rear face of this movable component while at the same time the cemented surface of the first stationarycomponent, i.e., the front component of the attachment, has a radius whose absolute magnitude is less than 1.5 times that of the radius of the convex forward face of this front component.

3,273,457 Patented Sept. 20, 1966 "ice A further feature of the objective referred to involves the construction of the associated basic objective which in accordance with this improvement has two image-side components of opposite refractivity whose mutual separation is less than 50% of the axial thickness of the negative one of these components. This arangement enables not only a very compact construction of the basic objective but also, by virtue of the relatively thick lens member, a favorable control of spheric and comatic aberrations.

In accordance with out instant invention, the absolute values of the focal lengths f f and f of the first, third and fourth lens members of the system (as seen from the object side) substantially satisfy the relation- The reduced displacement stroke realized by virtue of the above feature enables the objective to be so constructed, if this should be desired for the purpose of more convenient mounting, that the negatively retracting third component is stationary Whereas the positively refracting fourth component, i.e., the last member of the attachment, is movable to a limited extent. 7

In order to achieve good chromatic correction and maximum elimination of distortion, still another feature of the invention lies in dimensioning the first two radii r1, r2 of the compound front member in accordance with the relationship these two radii defining the more forwardly positioned positive lens of this doublet Whose refractive index for the yellow d line of the spectrum should be greater than substantially 1.65.

It is furthermore desirable, for a favorable correction of spherical aberration and suppression of astigmatism, to constitute the negatively refracting second component from two lens members, including a doublet preceding a singlet, and to proportion the radii of curvature r7 and r8 of that singlet according to the relationship In the accompanying drawing:

FIG. 1 illustrates a varifocal objective as disclosed in our prior application Ser. No. 209,866, now abandoned; and

FIG. 2 shows a similar objective incorporating the present improvement.

The objective shown in FIG. 1 comprises a varifocal attachment, constituted by four air-spaced components I-IV, and a basic or principal objective VI. Component I is a doublet composed of a positive lens L1, with radii r1, r2 and thickness d1, which is cemented onto a negative lens L2 having radii r2, r3 and thickness d2. Component II, separated from component I by a variable air space d3, is likewise a doublet consisting of a positive lens L3 (with radii r4, r5 and thickness d4) and a negative lens L4 (with radii r5, r6 and thickness d5) cemented to it. Another variable air space d6 intervenes between this movable member and the next likewise movable component III which is a single lens L5 with radii r7, r8 and thickness d7. The last component IV of the attachment, which follows component III by a further variable air space d8, is a positive singlet L6 with radii r9, r10 and thickness d9. The large air space between the attachment I-IV and the principal objective VI is partly occupied by a prism V of axial width d11, which is bounded by fiat surfaces designated r11 and r12, separated from lens L6 by a small air space d10 and from the fixed lens group VI by a larger air space d12 accommodating a diaphragm D. The basic objective VI consists of four air-spaced singlets including a positive lens L7 with radii r13, r14 and thickness d13, another positive lens L8 (radii r15, r16 and thickness d15) separated from the lens L7 by an air space d14, a negative third lens L9 with radii r17, r18 and a relatively great axial thickness d17, this lens being separated from lens L8 by the air space d16, and finally a positive fourth lens L10 (radii r19, r20 and thickness c119) whose separation d18 from the preceding lens L9 is less than half the thickness d17 of the latter.

The following Table A lists representative values for the individual focal lengths f of the components I, II, III, IV and VI, the radii r1 to r20 and the thicknesses and separations d1 to d19 (based upon a numerical value of 100 for the mean focal length of the system), the refractive indices n of the lenses L1 to L10 and their Abb numbers 1 the system so defined having an aperture ratio of 1:1.8, a back-focal length of 58.1 and a varifocal range from 50 to 200 units (i.e., millimeters).

4 composed of lenses L1, L2 (similar to lenses L1 and L2 of FIG. 1) with radii r1'-r3' and thicknesses d1'd2', Component II, separated from component I by a variable air space d3, comprises a doublet L3, L4 with radii r4-r6' and thicknesses d4'-d5', similar to the lenses L3 and L4 of component II in FIG. 1, and a biconcave singlet L5 (radii r7, r8, thickness d7) sep arated from that doublet by an air space d6. Another variable air space d8 intervenes between singlet L5 and the second negative component III which, similarly to component III of FIG. 1, is a singlet with radii r9, r10 and thickness d9. A further variable air space 1110' separates lens L7 from the fourth component IV' again consisting of a single positive lens L7 with radii r12, r13 and thickness d11. The air space d12' between member L7 and prism V' may be fixed or variable, depending on whether component III or component IV TABLE A Individual Focal Lens Radil Thicknesses m Lengths and Separations r1 =+275. 13 L1 d1=58. 75 1. 61772 49. 78 ([1) +478. 1 I r2 =-355. 69

(13:127. 19 Variable air space r4 =1821. 25 L3 d4=22. 50 1. 80518 25. 46 Un)-175. 7 II r5 =217.

d6=61. 00 Variable air space 142. 56 (hm-241. 9 111 L5 d7=6. 25 1. 62004 36. 34

d8: 66. 25 Variable air space r0 =+275. 63 (f1v)+236.6 IV L6 d9=12. 50 1. 52015 63. 59

d10=3. 13 Air space T11= on V d11=55. 00 1. 51680 64.

T12= co d12= 15. 63 Air space r13=+124. 00 L7 d13=l3. 75 1. 67790 55. 52

d14=0. Air space r15= +56. 31 L8 d15= 14. 88 1. 69680 55. 61

r16= +85. (fv1)+10i.4 VI d16=7. 50 Air space r17= -177. 50 L9 d17=19. 69 1. 78470 26. 10

d18=8. 13 Air space r19= +93. 00 L10 d19=14. 38 1. 74400 44. 90

dtotll=522. 93

The variation of the air spaces d3, d6 and d8 for the realization of different overall focal lengths] will be apparent from the following Table B:

The system shown in FIG. 2 is generally similar to that of FIG. 1 and consists of components I'- a prism is movable to compensate for the shifting of the image plane due to the displacement of component II. The remaining radii r13'-r22 and spacings or thicknesses d13'-d21' correspond substantially to the radii r11-r20 and thicknesses or separation d11-d19 of the system of FIG. 1 whose basic objective VI is similar to the objective VI of FIG. 2.

Representative values of the parameters r1'-f22' and d1-d21', the individual focal lengths f of components I'-IV' and VI and their refractive indices and Abb numbers of the system of FIG. -2 are listed in the following Table C, the aperture ratio being again 1:1.8 and the varifocal range remaining at 50 to 200 units; the

V' and a basic objective VI. Component I' is a doublet back-focal length is 58.25.

TABLE C Individual Focal Thicknesses Lengths Lens Radii and m w Separations r1 =+275.13 L1 (11 =54.38 1.66672 48.38 (11' +419.0 I r2 =-303.25

d3=107.18 Variable air space r4 +3312.50 L3 114 =16.88 1.80518 25.46

r5 =-241.75 L4 d5 =5.94 1.53913 61.24 (111') -112.5 II r6 =+169.06

d6 =14.38 Air spice r7 =531.88 L5 d7 =6.25 1.60311 60.68

d8 =77.31 Variable air space r9 =76.69 (mm-273.9 111' L6 119 =6.25 1.63636 35.35 r10=-140.56

d10=20.20 Variable air space r11=+625.25 (frv) +1744 IV L7 d11'=12.50 1.62230 53.14 112 -l3l.06

d12=16.12 Fixed or variable air space r13 w dl3=37.50 1.51680 64.20

r14'=ee d14'=18.94 Air space r15=+12l.19 L8 d15=13.75 1.67790 55.52

d16=0.25 Air space r17=+56.31 L9 d17=14.88 1.69350 53.39

rl8=+86.38 (fvr') +1021 VI d18=7.50 Air space L10 dl9'=19.69 1.230518 25.46

d20=8.13 Air space r2l=+93.00 L11 d21'=14.38 1.74400 44.90

totnl=48L16 The system of FIG. 2, 1n common with that of FIG. TABLE E 1, has a nearly piano-convex collective front component with a forwardly concave cemented surface (12 or r2) of strong negative refract1v1ty and a second component Which Includes a dispersive doublet with a forwardly 50 5.13 196,06 3.50 16.12 110.87 90131 16.50 3.13 concave cemented surface (r5 or r5 of strong posit ve 200 190.18 11.00 312 refractivity, the first-mentioned mternal radius having 50 an absolute magnitude which is less than 1.5 times that of the radius (r1 or r1) of the front surface of the first component whereas the second internal radius has an absolute magnitude less than 2.5 times that of the radius- TABLE D f as as (110 If member III remains fixed and member IV is movable, the air spaces d3, d8, d1()' and d12 will vary in accordance with the following Table E.

It will be understood that the width of the prism V is not critical in the system of Table C so that, particularly with fixed rear component IV of the attachment, the space dl2' will be substantially decreased (e.g., to the value given for space d10 in Table A) with a corresponding increase in the axial dimension of the prism; conversely, the prism may be omitted entirely if no reflex-type viewfinder is required. Moreover, as will be apparent from Table D, the varifocal range may be increased beyond the ratio of 4:1.

We claim:

1. An objective system comprising a principal objective and an attachment forwardly of said principal objective, said attachment consisting of four air-spaced components including an at most limitedly adjustable positive first component on the object side of the system, a negative second component following said first component, a negative third component following said second component, and a fixed positive fourth component following said third component and facing said principal objective;

' said negative second and third components being movable,

relatively to each other and to said first and fourth com-' ponents, into a first position in which the system has a relatively small focal length and a second position in which the system has a relatively large focal length; said second component having an individual focal length whose absolute value is less than that of the individual focal lengths of said first, third and fourth components and less than twice that of the focal length of said principal forwardly concave cemented surface having a radius of curvature whose absolute magnitude is less than 1.5 times that of the radius of said forward face, said second component including a doublet with a concave rear face and objective, said first component being a doublet with a a positively refracting forwardly concave cemented surconvex forward falce algd a nlegatively refiracting forwardly face hail'ing a; radziuss tof (illl'llllaltlll'ef ughosedabsoliite i iagniconcave cemente su ace aving a ra ms 0 curvature tu e is esst an imest a o t e ra ius o sai rear whose absolute magnitude is less than 1.5 times that of face, said principal objective consisting of four air-spaced the radius of said forward face, said second component singlets including two image-side lenses of opposite reincluding a doublet with a concave rear face and a posifractivity separated by an air space which is less than half tively reftiiactingf forwardly corlilcave cgmented surfacedhavtlllie 1axial tiliCkEgSS fof tfliefinetgative one tofthsaild lensis; ing a ra ius o curvature w ose a so ute magnitu e is t e enses o sai rs componen e enses less than 2.5 times that of the radius of said rear face, and L4 of said second component, said third component said principal objective consisting of four air-spaced L5, said fourth component L6 and the four air-spaced singlets including two image-side lenses of opposite resinglets L7, L8, L9, L10 of said principal objective havfractivity separated by an air space which is less than ing radii r1 to r10, r13 to r and thicknesses and spachalf the axial thickness of the negative one of said lenses; ings d1 to d19 whose numerical values, based upon a the separations d3, d6 and d8 each having a first value numerical value of 100 for the mean focal length of the corresponding to said first position and a second value system, along with the refractive indices n and the Abb corresponding to said second position: 20 numbers v of said components are substantially as given in the following table, the spacings d3, d6 and d8 being given for said third position:

Lens Radii Thicknesses and Separations 79.1 v

rl=+275.13 Lens Radii Thicknesses and m r L1--- 355 69 d1=58.75 1.61772 49. 78 Separations L2- d2=8.75 1.76180 26.98

'3= 3212'5o 615 (first osition) L1 fl=+m 13 d1-58 75 1 61772 49 78 4 182125 {2 14.52(sec nd position) space L2 r2=355. 69 (12 8 7 1'76180 26'98 L3 1 8 d4=22.5o 1.80518 25.46 r3=-32l2. 50 19 S 308 L4 r d5=7.50 1.62041 60.29 r4=l82l. 25 p r6=+102.06 18015 fir t m L3 5 217 00 d4=22. 50 1.80518 25. 46 T7 14256 {12190iseoddi osiiiion) Airspaie. L4 d5=7.50 1.620 41 60.29

T L5"... d7=6.25 1. 62004 35.34 d6=6l. 00 Air spice r8= 3618'75 6814 11m oiti L5 142'56 47 625 1 62004 3634 S S 011 56 {27.02 8656131 position Space r8=3618.75 d8 66 25 M s ace L6-- r9 +27 3 d9=12.50 1.52015 63.59 r9=+275.63 p

r10=220.31 L6 d9=l2.50 1.52015 63. 59

13 124 00 d10+d11+dl2=73.76 r10=220. 31 dm+dn+d12 73 76 L7.-. r d13=13.75 1.67790 55.52 r13=+124.00

r14=-47a.63 L7 d13=13. 75 1.67790 55.52

di4=0.25 Airspace r14=473.63 m 0 25 Air 5= 5 1 S 106 L8.. T1 63 d15=14.88 1.09080 55.61 rl5=+56. 31 p rl6=+85.50 4 L8 dl5=14.88 1.69680 55.61

. d16=7.50 Air space r16=+85. M6 7 50 Air s ace L9 177 50 d17=i9.69 1.78470 26.10 r17=177. 50 p r18=+46.84 L9 d17=l9. 69 1. 78470 26.10

d18=8.13 Airspace r18=+46.84 (118 8 13 Air ice 5 mm... 719 +93 00 a19=i4.a8 1. 74400 44. 90 50 r19=+93.00 p

r20=7l.94 L10 2o 71 94 d19=14.38 1.74400 44.90

2. An objective system comprising a principal objective and an attachment forwardly of said principal objective, A! g g slstem a Pgi 61min g g said attachment consisting of four air-spaced components compnslfng a a ffi i t Y a z including an at most limitedly adjustable positive first 5 1 :gf ex 2 i z component on the object side of the system, a movable an 2 fi 0 s Y negative second component following said first component, i Ween Sal attac em an P a negative third component f ll i Said second cipal ob ective with a separation d10 substantially equal ponent and a fi d positive f rth component fonowmg to 3.13 from sa1d fourth component L6 and with an axial said third component and facing said principal objective; thickness sflbstantlally q f said negative second and third components being movable, 4. An ob ective system comprising a principal ob ective relatively to each other and to said first and fourth com- 65 and an attachment forwardly of said principal ob ective, ponents, into a first position in which the system has a said attachment consisting of four air-spaced components relatively small focal length, a second position in which including an at most limitedly adjustable positive first the system has a relatively large focal length, and a third component on the object side of the system, a negative position in which the system has an intermediate focal second component following said first component, a negalength; said second component having an individual focal tive third component following said second component, length whose absolute value is less than that of the inand a positive fourth component following said third dividual focal lengths of said first, third and fourth comcomponent and facing said principal objective, said second ponents and less than twice that of the focal length of said component and one of the remaining components other principal objective, said first component being a doublet than said first component be1ng axially movable; said negative second and third components being movable, relwith a convex forward face and a negatively retracting atively to each other and to said first and fourth components, into a first position in which the system has a relatively small focal length, a second position in which the system has a relatively large focal length, and a third position in which the system has an intermediate focal length; said second component having an individual focal length i whose absolute value is less than that of the individual focal lengths f f f of said first, third and fourth components and less than twice that of the focal length of said principal objective, said first component being a doublet with a convex forward face and a negatively refracting forwardly concave cemented surface having a radius of curvature whose absolute magnitude is less than 1.5 times that of the radius of said forward face, said second component including a doublet with a concave rear face and a positively retracting forwardly concave cemented surface having a radius of curvature whose absolute magnitude is less than 2.5 times that of the radius of said rear face, the absolute values of the focal lengths f f f substantially satisfying the relationship 0.3]f 3(|f |-f l.3]f said third and fourth components each being a singlet, the radii r1, r2 of the front surface and the cemented surface of said first component substantially satisfying the relationship +1.2rl'-r2', said second component further including a biconcave singlet preceded by the doublet thereof, the radii r7 and r8 of the front and rear surfaces of said biconcave singlet substantially satisfying the relationship lr8g-r7.

5. An objective system comprising a principal objective and an attachment forwardly of said principal objective, said attachment consisting of four air-spaced components including an at most limitedly adjustable positive first component on the object side of the system, a negative second component following said first component, a negative third component following said second component, and a positive fourth component following said third component and facing said principal objective; said second component and one of the remaining components other than said first component being axially movable, relatively to each other and to the other two components, into a first position in which the system has a relatively small focal length, a second position in which the system has a relatively large focal length, and a third position in which the system has an intermediate focal length; said second component having an individual focal length f whose absolute value is less than that of the individual focal lengths f f f of said first, third and fourth components and less than twice that of the focal length of said principal objective, said first component being a doublet with a convex forward face and a negatively refracting forwardly concave cemented surface having a radius of curvature whose absolute magnitude is less than 1.5 times that of the radius of said forward face, said second component including a doublet with a concave rear face and a positively refracting forwardly concave cemented surface having a radius of curvature whose absolute magnitude is less than 2.5 times that of the radius of said rear face, said principal objective consisting of four air-spaced singlets including two image-side lenses of opposite refractivity separated by an air space which is less than half the axial thickness of the negative one of said lenses, the absolute value of the focal lengths f f f substantially satisfying the relationship said third and fourth components each being a singlet, the radii r1, r2 of the front surface and the cemented surface of said first component substantially satisfying the relationship +1.2rlZ-r2, said radii r1, r2 defining a lens with a refractive index n greater than 1.65 said second component further including a biconcave singlet preceded by the doublet thereof,'the radii r7 and r8 of the front and rear surfaces of said biconcave singlet substantially satisfying the relationship l0r8Z-r7.

6. An objective system as defined in claim 5 wherein the lenses L1, L2 of said first component, L3, L4 and L5 of said second component, said third component L6 said fourth component L7 and the four air-spaced singlets L8, L9, L10, L11 of said principal objective have radii rl to r12, r15 to r22 and thicknesses and spacing d1 to d21 whose numeral values, based upon a numerical value of 100 for the intermediate focal length of the system, along with the refractive indices n and the Abb numbers v of said components are substantially as given in the following table, the spacings d3, d8 and d10 being given for said third position:

Lens Radii Thieknesses and Sepanu v rations r1 275.13 L1 d1 54.38 1.66672 48.38

r2 303. 25 L2 3 1926 5 d2 8.75 1.80518 25.46

d3 =107. 18 Air space r4 =+3312.50 L3 d4 16.88 1.80518 25. 46

r5 241.75 L4 6 69 06 d5 5. 94 1.58913 61.24

d6 14. 38 Airspace r7 531.88 L5 8 +116 d7 6.25 1.60311 60.68

d8 77.31 Air space r9 76. 69 L6 d9 6.25 1.63636 35.35

d10= 20. 20 Air space r1l'= +625. 25 L7 12 131 06 d11'= 12.50 1. 62230 53.14

d12'+dl3+d14=72. 56 r15: +121.19 L8 16 518 63 d15= 13.75 1.67790 55.52

d16'= 0.25 Air space 117 +56. 31 L9 18 +86 38 (117: 14.88 1.69350 53.39

d18= 7.50 Alr space r19= 186. 81 L10. 20 +47 66 d19= 19.69 1.80518 25.46

d20= 8.13 Airspace r21= +93. 00 L11 2 73 00 d21= 14. 38 1.74400 44.

7. An objective system as defined in claim 6 wherein said third component is axially movable and said fourth component is fixed, further comprising a deflecting prism with plane forward and rear surfaces and with a refractive index n of substantially 1.51680 and an Abb number 1 of substantially 64.20 interposed between said attachment and said principal objective with a separation d12 substantially equal to 16.18 from said fourth component L7 and with an axial thickness d13 substantially equal to 37.50.

8. An objective system as defined in claim 7 wherein the separations d3, d8 and d10 have substantially the values 5.13, 196.06 and 3.50, respectively, in said first position and 190.25, 11.44 and 3.00, respectively in said second position.

9. An objective system as defined in claim 5 wherein the lenses L1, L2 of said first component, L3, L4 and L5 of said second component, said third component L6, said fourth component L7 and the four air-spaced singlets L8, L9, L10, L11 of said principal objective have radii r1 to r12, r15 to r22 and thicknesses and spacings d1 to d21 whose numerical values, based upon a numerical value of for the intermediate focal length of the system, along with the refractive indices n and the Abb numbers 11 of said components are substantially as given in the following table, the spacings d3, d8 and d10 being given for said third position:

Lens Radil Thlcknesses and Sepam u rations r1 275.13 L1 d1 54.38 1.66672 48. 38

r2 303. 25 L2 I (12 8.75 1.80518 25. 46

d3 =110. 87 Air sp ace r4 =+3312. 50 L3 d4 16.88 1.80518 25. 46

r5 241. 75 L4 I +169 06 d5 5. 94 1.58913 61. 24

d6 14. 38 Air sp ace r7 531.88 L5 I 0 d7 6.25 1.60311 60.68

d8 90.31 Airspace r9 76.69 L6 d9 6.25 1.63636 35.35

' d10'= 16.50 Air space r11=+ 625.25 L7 12 131 06 1111 12.50 1.62230 53.14

d12+d13'+d14=59. 57 r15=+ 121.19 L8 4115: 13.75 1.67790 55.52

7116': 0.25 Airspace r17'=+ 56.31 L9 18 86 38 (117: 14.88 1.69350 53.39

d18= 7.50 Air sp 108 r19=- 186.81 -L10'---- 20 +47 66 d19= 19.69 1.80518 25.46

d20= 8.13 Airspace r21=+ 93.00 L11--.- 22 73 00 d21= 14. 38 1. 74400 44. 90

10. An objective system as defined in claim 9 wherein said third component is fixed and said fourth component is axially movable, further comprising a deflecting prism with plane forward and rear surfaces and with a refractive index n of substantially 1.51680 and an Abb number v of substantially 64.20 interposed between said attachment and said principal objective with a separation d14' substantially equal to 18.94 from said principal objective and with an axial thickness d13' substantially equal to 37.50.

11. An objective system as defined in claim 10 wherein the separations d3, d8, and d12' have substantially the values 5.13, 196.06, 3.50 and 16.12, respectively, in said first position and 190.18, 11.00, 3.12 and 16.51, respectively, in said second position, the value of d12 in said third position being substantially 3.13.

References Cited by the Examiner UNITED STATES PATENTS 2,847,907 8/1958 Angenieux 8857 3,027,805 4/1962 Yamahi 88-57 3,057,257 10/ 1962 Klemt et al. 88-57 JEWELL H. PEDERSEN, Primary Examiner.

JOHN K. CORBIN, Examiner. 

1. AN OBJECTIVE SYSTEM COMPRISING A PRINCIPAL OBJECTIVE AND AN ATTACHMENT FORWARDLY OF SAID PRINCIPAL OBJECTIVE, SAID ATTACHMENT CONSISTING OF FOUR AIR-SPACED COMPONENTS INCLUDING AN AT MOST LIMITEDLY ADJUSTABLE POSITIVE FIRST COMPONENT ON THE OBJECT SIDE OF THE SYSTEM, NEGATIVE SECOND COMPONENT FOLLOWING SAID FIRST COMPONENT, A NEGATIVE THIRD COMPONENT FOLLOWING SAID SECOND COMPONENT, AND A FIXED POSITIVE FOURTH COMPONENT FOLLOWING SAID THIRD COMPONENT AND FACING SAID PRINCIPAL OBJECTIVE; SAID NEGATIVE SECOND AND THIRD COMPONENTS BEING MOVABLE, RELATIVELY TO EACH OTHER AND TO SAID FIRST AND FOURTH COMPONENTS, INTO A FIRST POSITION IN WHICH THE SYSTEM HAS A RELATIVELY SMALL FOCAL LENGTH AND A SECOND POSITION IN WHICH THE SYSTEM HAS A RELATIVELY LARGE FOCAL LENGTH; SAID SECOND COMPONENT HAVING AN INDIVIDUAL FOCAL LENGTH WHOSE ABSOLUTE VALUE IS LESS THAN THAT OF THE INDIVIDUAL FOCAL LENGTHS OF SAID FIRST, THIRD AND FOURTH COMPONENTS AND LESS THAN TWICE THAT OF THE FOCAL LENGTH OF SAID PRINCIPAL OBJECTIVE, SAID FIRST COMPONENT BEING A DOUBLET WITH A CONVEX FORWARD FACE AND A NEGATIVELY REFRACTING FORWARDLY CONCAVE CEMENTED SURFACE HAVING A RADIUS OF CURVATURE WHOSE ABSOLUTE MAGNITUDE IS LESS THAN 1.5 TIMES THAT OF THE RADUIS OF SAID FORWARD FACE, SAID SECOND COMPONENT INCLUDING A DOUBLET WITH A CONCAVE REAR FACE AND A POSITIVELY REFRACTING FORWARDLY CONCAVE CEMENTED SURFACE HAVING A RADIUS OF CURVATURE WHOSE ABSOLUTE MAGNITUDE IS LESS THAN 2.5 TIMES THAT OF THE RADUIS OF SAID REAR FACE, SAID PRINCIPAL OBJECTIVE CONSISTING OF FOUR AIR-SPACED SINGLETS INCLUDING TWO IMAGE-SIDE LENSES OF OPPOSITE REFRACTIVITY SEPARATED BY AN AIR SPACE WHICH IS LESS THAN HALF THE AXIAL THICKNESS OF THE NEGATIVE ONE OF SAID LENSES; THE SEPARATIONS D3, D6 AND D8 EACH HAVING A FIRST VALUE CORRESPONDING TO SAID FIRST POSITION AND A SECOND VALUE CORRESPONDING TO SAID SECOND POSITION: 